From a security perspective, my gut tells me this would make sense, but I don't think it would be a very Mozilla thing to do.

What do you guys think? Would it make sense to do this or would it be better to simply leave folk to their madness? Would giving them a notification be worth it (e.g. pop-up or special highlighting in about:addons)?

P.S. - I'm talking about current extensions and not pre-WE ecosystem. The extension I'm being nit-picky about is StumbleUpon and it was ported over to WE. Because they abandoned ship, the extension has since been removed from add-on site.

Is this a trick question? Users should be in charge of their own user-space. Corporations should not be mucking around it without specific consent because that is a very slippery slope down which we have already slipped too far.

Anyhow, a "compatible" extension, just because it's no longer listed on AMO (who would trust anything there anyhow) is no reason for it to be removed (by Mozilla) from your browser. (Though if Mozilla were to do that, it would be a very Mozilla-like thing for them to do.)

Two thoughts about that. First is that if they were removed when Quantum first came out I would have expected a huge outcry from users who didn't keep track of which extensions they had been using. Second, another group of users would have complained that Mozilla shouldn't have removed them; plus removal would have made it impossible to revert to an earlier version of Firefox and pickup with the older version where they had left it. Not withstanding what ever incompatibility "going back" might have entailed.

As far as the security aspects if leaving old, no longer supported extensions on Firefox; what's the difference? If an extension is disabled due to incompatibly it isn't going to be doing anything except for taking up space.

OMO, the bottom line is that if an extension is no longer compatible just disabled it and note the reason. That was done by Mozilla.

Then as far as legacy extensions being removed from the Addons.Mozilla.Org website. They remained there until a few versions of Firefox Release version beyond the last ESR version which those extensions worked in. In my mind the timing for their removal was 'spot on' for them to disappear.

A mind is a terrible thing to waste. Mine has wandered off and I'm out looking for it.

Then as far as legacy extensions being removed from the Addons.Mozilla.Org website.

Thee was a deadline where new legacy extension could be inserted, and another deadline 6 month after for available legacy extension to be updated the last time. some authors deleted due this their extension, or they went webextension. i forgot if or when mozilla will delete legacy extension at all. for now they did nothing, it was all about authors. the given timeline is not valid:https://blog.mozilla.org/addons/2018/08 ... x-add-ons/

We're not talking about Legacy.We're talking about a webextension which is no longer listed on AMO.

(AMO regularly blanket removes malware (web)extensions - once they become aware of them [& blacklists them, thereby disabling them from your browser - which is fine]. But I take it that that is not the reason for StumbleUpon's absence.)